1993 Bobcat 843b bleeding down

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cmreckard

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Sep 23, 2022
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Hi Guys, I am a home builder and have operated plenty of equipment but am new to owning and repairing anything other than trucks and trailers.
That being said, I bought an 843b at auction and have sunk a ton of money into an ancient machine at this point. I've pretty much got the thing operating well and leak free but am still having trouble with the hydraulics bleeding down (even while the machine is still running) and the biggest problem is that my 4N1 bucket will stay shut tight but not hold open unless I disconnect it from the machine.
The boom and tilt leak down slowly (which is tolerable) but the auxiliary seems to have an issue that is more than normal wear going on.
Also if I switch the hoses on the bucket it will hold open but not stay closed tight.
Anyone got any suggestions?
Been tough for me to find anyone local that has ever worked on something of this vintage.
 

brdgbldr

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Jun 1, 2012
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You might want to check your auxiliary valve. It sounds like one side needs new seals. All of your valves could need new seals and that is why your lift and tilt won't hold also.
 
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cmreckard

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Sep 23, 2022
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Would that be the spool seals you are talking about? I assumed that you would see the control valve leaking if they were bad, but if they leak or allow oil to bypass would they leak internally?
 

brdgbldr

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I am talking about the spool seals. I used that as a general statement that you should check the auxiliary spool. There are other parts like the detent balls and springs that could be corroded or missing that cause problems. Let alone the actual spool could be bad.
 
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cmreckard

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I am assuming that the detents are working and free because the aux will still lock in if I push all the way to the right and the float mode is still working great on the boom. I don't see any leaks from the control valve. Machine has just over 1000 hours on it and was state maintained. Is it possible that there is a check valve or something simple that could be boogered up? I really thought it was going to be the cylinder seals in the bucket when I bought it but they are holding fine apparently. Hate to take apart that control valve haha. It doesn't look fun to get at on this machine.
Thanks for your input
 

brdgbldr

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Bleed down can be caused by a variety of things. Anything from bad seals to a worn out pump. Some bleed down is exceptable. Bobcat has an inch per hour rating (that of course I can't find right now, it was like a couple of inches per hour with the machine off) that they only recommend correcting if it goes over it.

The auxiliary only working in one direction could also be as simple as a bad, or loose, linkage on a mechanical machine.

You need to look at your specific machine. There were a few different setups for auxiliaries on 843's.
Go to the Bobcat parts website:

Enter in your serial number and then search "auxiliary". This will bring up all of the exploded views with any part that has the word "auxiliary" in it. Some of the 863's had a separate auxiliary section, which may or may not be easy to get to.

You may also want to look at the hand controls exploded view and trace them in your machine to see if any of the linkages for the auxiliary are loose, broken or bent. I've had machines where bolts have rattled loose and disappeared. Take a good look at any bolts that go through slots. These, at first glance may look ok and tight, but when you move the controls they may slip. You may need a helper to move the auxiliary control lever back and forth while you look at the linkages and valves.

This should give you a good place to start. Also, a lot of machanics do not remove the control valve to work on them. I also sudgest looking at videos online of any bobcat control valve or spool work. The valves are more or les similar, and it will give you a good idea of how much or little work it will take to rebuild one.
 

spitzair

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Dec 17, 2009
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Brdgbldr has some excellent starting points here. Another thing to look at is load check valves on the spool valve itself, if they go bad they can cause it to do exactly what you describe. Having said that I don't know if an 843 has them as I've never worked on one…
On edit I just looked at the parts diagram and the 843 does have them above serial number 503724001 which I assume yours is being that it's an 843B.
 
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cmreckard

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Sep 23, 2022
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I was just out at my shop looking at that control valve. The linkage seems to be pretty tight on the auxiliary. detent seems to function properly but I wasn't sure where the check valve would be for that. Is there a ball and spring under a plug? Also, the valve looks really fun to reach the backside of haha. I'm 6'3 and can hardly touch it with my fingertips unless the motor is pulled
The boots are in tough shape on the front of the valve but I don't see anything leaking external front or back.
 
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cmreckard

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I believe my machine is one of the last year models of the 843 so its in the upper serial numbers on the bobcat catalogue.
Looking at the diagram I'm not sure what load check valve corresponds with the auxiliary spool but I would be tickled if it was something simple to clean the junk out of or replace that is causing this issue. That bucket isn't very useful if you cant use it as a box blade or a grapple
 
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